Abstract

When used to treat lung cancer, intensity-modulated radiotherapy (IMRT) can deliver higher dose to the targets and spare more critical organs in lung cancer than can 3-dimensional conformal radiotherapy. However, tumor-motion management and optimized radiotherapy planning based on 4-dimensional computed tomography scanning are crucial to maximize the benefit of IMRT and to eliminate or minimize potential uncertainties. This article summarizes these strategies and reviews published findings supporting the safety and efficacy of IMRT for lung cancer.

Intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) can spare more critical structures than can three-dimensional conformal radiotherapy (3DCRT) in the treatment of a bulky stage III non-small cell lung cancer (NSCLC) tumor located near the esophagus and heart. Top row, 3DCRT cannot safely be used to deliver a definitive dose (60 Gy) because it results in an unacceptably high total mean lung dose (21 Gy), heart dose (V40=43%). Second row, Limited intensity modulation using the same four beam angles as are used in 3DCRT (IMRT-3D; dashed lines) resulted in improved sparing of lung, heart, and esophagus, particularly in the low-dose region. Although IMRT-3D is not an ideal solution in this case, IMRT-3D could be similar to or better than 3DCRT in terms of sparing critical structures if the same beam angles are used. (Even in the worst case, one can always choose to not modulate intensity if that would increase the dose to critical structures of interest.) Third row, Optimized IMRT using 9 beam angles (IMRT-Op) further improves sparing of critical structures, particularly the heart. Note that target conformality is compromised in IMRT-Op in order to spare more heart and contralateral lung. Bottom row, Optimized IMRT (9 beam angles) and VMAT (2 arcs) produce similar critical normal tissue sparing in this case.